Precision forming of titanium alloys and the like by use of induction heating

ABSTRACT

Titanium alloy blanks or the like are successively coated with a high-temperature lubricant; preheated, e.g. in a preheat oven or in the forming machine, to a forming temperature (about 1000 1775* F.); precision formed into a desired shape in a press which includes inductively heated forming tools, serving to maintain the metal at the forming temperature throughout the forming operation; and slowly cooled, e.g. first in a postheat oven down to a lower elevated temperature (e.g. about 600* F.) and then down to ambient temperature under cover of an asbestos blanket or the like. The heat-forming tools include a fixed die, a movable die and a movable clamping pad. The movable tools are mounted for precision movement by leader pins and bushings. Insulation and water jackets are interposed between the heated tools and the leader pins and bushings to prevent harmful heating of the latter. The forming tools comprise water-cooled tubular conductors embedded in insulative material which in turn is embedded in die parts of long life metals on which the forming surfaces are machined or embedded in supporting cores therefor.

Arne H. Carlson 5534 South 119th, Seattle. Wash. 98178 [72] Inventor{2|} Appl.No. 791,553 [22] Filed Jan. 16, I969 [45] Patented June 15,1971 Continuation-impart of application Ser. No. 702,700, Feb. 2, I968.

[54] PRECISION FORMING OF TITANIUM ALLOYS AND THE LIKE BY USE OFINDUCTION HEATING 26 Claims, I6 Drawing Figs.

Primary Examiner- Lowell A. Larson AuorneyGraybeal, Cole and BarnardABSTRACT: Titanium alloy blanks or the like are successively coated witha high-temperature lubricant; preheated, e.g. in a preheat oven or inthe forming machine, to a forming temperature (about 1000 l775 F.);precision formed into a desired shape in a press which includesinductively heated forming tools, serving to maintain the metal at theforming temperature throughout the forming operation; and slowly [52]US. Cl 72/38, cooled, first in a postheat oven down to a lower elevated72/342 72/364 72/700 temperature (e.g. about 600 F.) and then down toambient [51] Int. Cl B2111 37/16 temperature under cover of an asbestosblanket or the i [50] Field of Search 72/342, The h t f i took include afi d die, a movable die A 56; 148/115 and a movable clamping pad. Themovable tools are mounted for precision movement by leader pins andbushings. Insula- [56] References cued tion and water jackets areinterposed between the heated tools UNITED STATES PATENTS and the leaderpins and bushings to prevent harmful heating of 1,380,250 5/1921 Reymond72/342 the latter. The forming tools comprise water-cooled tubular2,247,979 7/1941 Von Tannenberg.. 219/7.5 conductors embedded ininsulative material which in turn is 2,372,516 3/1945 Rechton et al72/342 embedded in die parts oflong life metals on which the forming2,449,365 9/1948 Bober et al. 219/75 surfaces are machined or embeddedin supporting cores 2,890,324 6/1959 l-lavlik 2l9/I49 therefor.

M f" Moi mo r k /52 7 ma 41 1 S\\ VIII/VIII III "1 m, l 4 l PATENTED Jmn5197i SHEET 3 OF 5 RL 0?, N M Wm mum m A PRECISION FORMING OF TITANIUMALLOYS AND THE LIKE BY USE OF INDUCTION HEATING CROSS-REFERENCE TORELATED APPLICATION This is a continuation-in-part of my copendingapplication Ser. No. 702,700, filed Feb. 2, 1968, and also entitledPrecision Forming of Titanium Alloys and the Like By Use of InductionHeating.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a method and apparatus for hot pressure forming titaniumalloy blanks and the like. It particularly relates to forming equipmentcomprising movable forming tools which are mounted and guided forprecision movement by leader pins and bushings, and to a manner ofadequately heating the blanks while in the forming equipment withoutinjuriously heating the leader pins and bushings.

2. Description of the Prior Art Bridwell U.S. Pat. No. 3,015,292 andHaerr U.S. Pat. No. 3,025,905 both discuss the difficulties ofpressure-forming titanium alloy blanks. They both explain that suchblanks must be heated to a relatively high temperature before they canbe formed into a desired shape, and each suggests heating the blanks bymeans of resistance heaters incorporated in the forming equipment.

Resistance heaters are unsatisfactory for this purpose for severalreasons. They experience uneven heat distribution resulting in theoccurrence of hot spots and an uneven heating of the forming surfaces,causing them to warp. This results in the production of nonuniform partswhich in many instances are inferior and unusable. Furthermore,high-temperature resistance heaters customarily burn out frequently andthus require frequent replacement. Besides being expensive, thisfrequent replacement of the heaters amounts to a frequent alteration ofthe forming equipment and is a contributing factor to a shortened lifeof both the replacement heating elements and the forming tools. This isbecause the heating element channels become enlarged somewhat duringeach heating element replacement. As a result, an air space is createdabout at least a part of the new heater element. Since air is a poorconductor the new heater elements tend to become overheated in use andburn out quickly. Also, the tools are not suitably heated. Replacementof the tools is necessary to correct a reoccurrence of these happenings.

Further examples of known forming machines which utilize resistanceheaters are shown by: Shoebridge et al. U.S. Pat. No. 2,956,148; SwainU.S. Pat. No. 3,051,830; Scott U.S. Pat. No. 3,065,331; and Kennedy U.S.Pat. No. 3,080,473. The machines disclosed by these patents are adaptedfor dimpling and other low order forming operations not involving theuse, heating or precision movement of relatively large area formingtools.

Corral U.S. Pat. No. 3,060,564 and Johnson et al. U.S. Pat. No.3,169,156 are examples of the oven and open flame types of installationsfor forming titanium alloys which are mentioned in the above discussedBridwell patent.

Manson U.S. Pat. No. 1,725,465 and Von Tannenberg U.S. Pat. No.2,247,979 disclose forming presses which utilize inductively heateddies. However, Manson is concerned with drying pulp articles, such aspaper pie plates, and Von Tannenberg is concerned with forming magnesiumalloy plates at temperatures ofonly about 320i10 C.

SUMMARY OF THE INVENTION Basically, this invention relates to theprecision forming of parts from titanium alloy blanks or the like by useof inductively heated forming tools, at least some of which are mountedand guided for precision movement by leader pins and bushings, and tothe use of some sort of heat barrier means between the heated componentsand the leader pins and bushings, to prevent injurious heating of thelatter. Other metals to which the invention is applicable, in additionto titanium alloy metals, are Hastoloy, hard to form aluminum alloys,and stainless steel or other steel parts requiring multiple draws.

According to a method aspect of the invention the blanks are firstcleaned and are then coated with a high-temperature lubricant capable ofwithstanding the forming temperature of the particular alloy involved(about 1000 1 755 F. for most titanium alloys, for example). Next theblanks are preheated to the forming temperature, such as in a preheatoven contain ing a noncorrosive atmosphere (e.g. argon for titaniumalloys which must be heated in a nitrogen-free atmosphere to avoidsurface contamination or corrosion of the metal), for example. Theblanks are successively removed from the preheat oven and are thenplaced in the forming equipment in contact only with the heated formingtools, which are at the forming temperature. Alternatively, the blanksmay be preheated in the forming equipment.

Following the forming operation the formed part is removed from theforming equipment and allowed to slowly cool down to room temperature.By way of typical and therefore nonlimitive example, the parts may beslowly cooled, first in a postheat oven down to the oven temperaturewhich is constantly maintained at a specific level (e.g. 600 F. for sometitanium alloys). Then, they are placed on an asbestos pad or the like,are covered by an asbestos blanket or the like, and are allowed toslowly cool down to room temperature. During the short period betweenthe two ovens, and at any other time when the parts are exposed to thecorrosive room atmosphere surrounding the equipment, they are adequatelyprotected by the lubricant coating.

Preferably, the forming equipment of this invention comprises a fixedforming tool and two movable forming tools which are supported by commonleader pins and their own bushings for precision movement along a pathbordering the fixed forming tool. Each blank is individually placed inthe equipment with a first portion thereof between the two movable toolsand an adjacent second portion in position to contact the fixed formingtool. Then the two movable tools are moved relatively together to clampand hold between them the first portion of the blank. Next, the twomovable tools and the blank are moved together as an assembly relativelytoward the fixed forming tool. The rate of movement is controlled sothat the heated blank undergoes plastic deformation unattended byappreciable strain hardening. During this operation the lubricantcoating functions as a lubricant and permits slippage of the blanklaterally of the direction of press movement, within the narrow spacewhich exists between the two movable forming tools. The blanks arepermitted only this single degree of movement and are restrained againstall other movement by the clamping surface of the two movable tools,

When forming a titanium part, at least, the temperature of the fixedtool (i.e. the forming punch) should be kept below (e.g. 50100 F. lower)the temperature of the two movable tools (i.e. the pressure pad and thedie). This is easily accomplished by providing each tool with its ownindependently controlled energy source, with each control circuitincluding a temperature sensor adapted to measure the temperature of itstool and send a control signal to means in the energization circuit formaking any adjustment which may be necessary to maintain the temperatureof the associated tool at its desired temperature level. Thisdifferential heating of the tools results in the material which is heldby the two movable parts being at a higher temperature, and hence moreductile, than the material which is in contact with the punch. As aresult, during forming a greater amount of material flow occurs in theclamped region than in the forming region, i.e. the region in contactwith the punch, and thinning of the workpiece in the forming region isthus minimized.

Preferably, each movable formimg tool is a part of an assembly whichalso includes a plurality of spaced-apart bushing housings containingguide bushings which surroundingly engage the leader pins, and crossframe means rigidly interconnecting said bushing housing. The leaderpins are rigid members and are firmly secured to a rigid support. Thebushings are precision made so they snugly engage the leader pins andare not free to wobble. The cumulative result of these features is thatessentially all parts of the tool assembly always move together and eachsequence of movements along the leader pins is essentially identical toeach other sequence of movements. This essentially eliminates theoccurrence of any nonuniformity amongst the parts as a result of changesin position and/or alignment of the forming surfaces. The bushings andthe lubricants used on them cannot withstand the high-formingtemperatures. Accordingly, a heat barrier in the form of a body ofinsulative material and/or a cooling jacket is interposed between theheated components of the tool and the bushings and leader pins. In thismanner the bushings and leader pins are maintained relatively cool andare protected from the injurious or destructive effects of the hightemperatures existing in the region of the forming tool.

The cross frame which rigidly interconnects the bushing housing supportsor carries the forming tool and the heat barrier means. According to oneform of the present invention the forming tool comprises an inductivelyheated core unit and a hard metal die part secured to the core unit, tobe conductively heated thereby. The core unit comprises a conduc torcoil (or plural coils), disposed within or encircling a support core.Preferably, the coil(s) are encased in a cast body of insulation whichis in turn at least partially encased by the core material (e.g. aferromagnetic material). In another form of the invention the supportcore is eliminated, a large piece of the die material is used, andchannels for receiving the conductor coils are formed in the diematerial.

The tubular conductor material, which may be copper tubing, is fashionedinto a coil (or multiple coils) which in form closely approximates theshape of the forming surfaces. The core is also formed to closelyconform to the shape of the forming surfaces.

Owing to this arrangement of the conductor and the core there is asubstantially even distribution of electrical energy throughout the coreunit. The conductor is not directly heated by the current it carries asis a resistance heater coil. However, due to its location it issusceptible of being conductively heated by the inductively heated coreunit. For this reason the conductor is made tubular in form and acooling fluid is flowed through it to remove the heat, and preferably itis also encased by insulation. This results in the conductor havingrelatively low operating temperature, and as a result a relatively longuse life. Any uneven heating of the core which might occur is bufferedby a dispersion of the generated heat throughout first the core unit,and then the die part to the forming surfaces. This results in asubstantially uniform or even heating of the forming surfaces andcontributes greatly to the obtainment ofsubstantially uniform parts.

Preferably, the heat barrier means includes a cooling jacket that isintegrated into wall portions of the aforementioned cross frame.Preferably also, the entire forming equipment, including the leader pinsand the fixed forming tool, is adapted to be placed between and clampedto the platens of a generally conventional forming press.

These and other inherent objects, features, advantages andcharacteristics of the present invention will be apparent from thefollowing description of typical and therefore nonlimitive embodimentsof the invention, as described below in conjunc tion with theaccompanying illustrations.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings like elementdesignations refer to like parts, and:

FIG. 1 is a diagrammatic view showing in sequence the four majoroperations which characterize the preferred method of this invention;

FIG. 2 is a front elevational view of a forming press equipped with drawforming equipment embodying features of the invention;

FIG. 3 is an enlarged scale sectional view, with some parts in sideelevation, of the central portion of the forming press shown by FIG. 1,taken substantially along line 3-3 of FIG. 4;

FIG. 4 is another enlarged scale sectional view, with some parts in sideelevation, of said central portion of the forming press shown by FIG. I,but taken substantially along line 44 of FIG. I;

FIG. 5 is an isometric view of a part formed by the draw formingequipment of FIGS. 24;

FIG. 6 is an isometric view ofa part formed by the forming equipment ofFIGS. 7 and 8;

FIG. 7 is a view similar to FIG. 3, but of a press equipped withwipe-forming equipment;

FIG. 8 is a vertical sectional view taken substantially along line 8-8of FIG. 7;

FIGS. 9l2 are four operational sequence views of the draw formingequipment of FIGS. 2-5, with FIG. 9 showing the movable forming toolsspaced apart and a preheated blank between them in position for forming,with FIG. 10 showing the two movable tools moved together to clampbetween them the peripheral portion ofthe blank, with FIG. ll showingthe two movable tools and the clamped blank in the process of beingmoved in unison, as an assembly, toward the stationary tool or punch,and with FIG. 12 showing the movable tools apart, the upper tool raised,and the central knockout element depressed to push out the formed part;and

FIGS. I3l6 are four operational views of the forming equipment of FIGS.7 and 3, with FIG. 13 showing the movable forming tools spaced apart anda preheated blank between them in position for forming, with FIG. 14showing the two movable tools moved together to clamp between them aside portion of the blank, with FIG. l5 showing the two movable toolsand the blank being moved towards the stationary tool or punch, and withFIG. 16 showing the two tools raised and again spaced apart and theformed part spaced outwardly to one side ofthe forming equipment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a preliminary step in thepreferred process of this invention, the titanium alloy blanks 10 aredeburred and polished, or are otherwise suitably cleaned. They are thensprayed or otherwise coated with a suitable high-temperature lubricant(i.e. a lubricant capable of withstanding the forming temperature), suchas Everlube T-SO, a graphite base lubricant manufactured by EverlubeCorporation of America having a place ofbusiness at North Hollywood,California.

Referring now to FIG. 1, following their lubrication the blanks areslowly heated, such as in a preheat oven 12, up to the formingtemperature, which temperature is in the range of about lOO0l775 F. fortitanium alloys. If heated to temperatures of this order in an airatmosphere (without being covered by a highly efficient coating), thetitanium metal would attract nitrogen and other contaminants from theair which would chemically combine with the metal and contaminate orcorrode its outer surfaces. Therefore, a noncorro sive or nitrogen freeatmosphere is provided and maintained in the oven during the heating.Argon is an example ofa suitable gas for use in the oven 12 to providesuch an atmosphere.

The preheated blanks 10 are successively removed from the preheat oven12 and set into the forming equipment, such as by a workman using tongsand asbestos gloves, and are then pressure formed, in a manner to behereinafter described in more detail. The blanks 10 are then slowlycooled to prevent severe (i.e. untolerable surface checking or cracking.

At least with relatively thick parts, the cooling is preferablyconducted in two stages. Firstly, the formed parts 10' are placed into apostheat oven 16 which is maintained at a specific elevated temperaturebetween ambient temperature and the forming temperature (e.g. about600700 F. for

titanium alloys) and also contains a noncorrosive atmosphere, such asargon, and are allowed to slowly and naturally cool in such oven 16 downto the oven temperature. The formed parts are then removed from thepostheat oven 16, are placed on an asbestos board or pad 18, and thenare quickly covered by an asbestos blanket 20. So covered, they areallowed to slowly and naturally cool down to ambient temperature. Thistwo stage cooling amounts to a simplified manner of slowing down thecooling process of the parts from the high-forming temperature toambienttemperature. to avoid the aforementioned surface cracking which wouldresult if rapid cooling were permitted. With thinner parts the coolingcan be done under the asbestos blanket alone.

During the intervals that the heated blanks 10 are between the preheatand postheat ovens l2, l6 and the heated parts 10' are between thepostheat oven 16 and the asbestos board 18, (or in the situation wheresuch ovens are not used) and such blanks 10 or parts 10' are exposed toair, the lubricant serves as a protective coating and protects the metalagainst contamination.

After cooling, the parts are cleaned and trimmed and are otherwisemachined to desired final form.

Referring now to FIG. 2, the forming press 14 is shown to comprise arigid-main frame 22 including a set of corner columns 24 rigidlyinterconnected at the top by upper crossmembers 26 and at the bottom bylower crossmembers 28. Husky intermediate crossmembers 30 areinterconnected between intermediate portions of the columns 24 andfunction as a support table or platform for the fixed platen 32 of thepress 14. A second set of intermediate crossmembers 34 are located abovethe movable platen 36 and serve to lend rigidity to the main frame 22 atsuch location.

The lower end portions of a plurality of parallel, husky guide pins 38are firmly anchored in outer portions of the fixed platen 32. Themovable platen 36 carries a set of guide bushings 40 which surroundinglyengage the guide pins 38.

A primary hydraulic ram 40 is suspended from a central location on theupper end portion of the frame 22 with the piston rod 42 thereofdirected downwardly. The lower end of the piston rod 42 is secured tothe movable platen36. The primary ram 40 is employed to raise and lowerthe movable platen 36, with the guide pins 38 and the bushings 40serving to maintain proper alignment of the movable platen 36 during itsmovement.

A secondary hydraulic ram 44 is supported below the intermediate supporttable 30 substantially in line with the upper ram 40. lts piston rod 46is directed upwardly and carries at its upper end a support pad 48 ofsubstantial area. The secondary ram 44 serves to apply a controlledbiasing force on a floating portion of the forming equipment,hereinafter to be described. A support shelf 50 is bracketed out fromthe main frame 22 on each of its two sides and at its rear, to eachsupport one of three transformers 52 powered by generator-driveninduction heat stations, which are conventional per se and not shown. InFIG. 2, which is a view looking toward the front of the machine, onlythe two side transformers 52 are shown. The third transformer 52 and itssupport shelf 50 are located to the rear of the press 14 and are thushidden from view. The lower support table which carries thelowermounting 54 for the secondary ram 44 may also serve to mountcomponents of the hydraulic system, such as the hydraulic pump 56 andan'electric motor 58 for driving the pump 56. Alternatively, theseaccessories and others may be located in a console or the like which isapart from the press 14.

The precision forming equipment of the present invention will now bedescribed. The particular forming equipment shown by FIGS. 3 and 4 is ofthe draw-forming type while the forming equipment shown by FlGS. 7 and 8is of the wipe"- forming type. However, as will be evident as thedescription of these two types of equipment progress, both tubes arebasically similar.

Referring now to FIGS. 3 and 4, the forming equipment is shown tocomprise a die set composed of a lower or fixed bolster plate 60, anupper or movable bolster plate 62, and a pair of leader pins 64. The twobolster plates 60, 62 may be fabricated from aluminum alloy and theleader pin 64 may be fabricated from stainless steel. A pair of socketsare formed in outer edge portions of the lower bolster plate 60 toreceive the lower end portions of the leader pins 64. The lower endportions of the leader pins 64 are tightly received in such sockets sothat the leader pins 64 are firmly held in parallelism. Bearing, sleevesor housings 66, carried by the movable bolster plate 62, house bronzebushings 68 or the like, which snugly surroundingly engage the leaderpins 64.

The upper bolster plate 62 is in some manner removably secured to themovable platen 36 and the lower bolster plate 60 is in a like mannersecured to the fixed platen 32. By way of typical and thereforenonlimitive example, the bolster plates may be secured to the platens byclamp assemblies C which are carried by the latter and include clampingplates 70 shown in FIGS. 24 to overlap border portions of the bolsterplates 60, 62. The die set, i.e. the two bolster plates 60, 62 and theleader pins 64, constitute the support portion of the forming equipment,making such equipment structurally self-contained. This feature, plusthe use of the clamps for removably securing the bolster plates totheplatens of the press, makes it easy to selectively use a number ofdifferent forming equipment assemblies, each possessing similar bolsterplates, within a single press.

The draw-forming equipment of FIGS. 3 and 4 comprises two movable toolsand one fixed tool, each of which is inductively heated as willhereinafter be explained in detail, and may include a knockout punch 72.One of the movable forming tools is a cavity die and is mounted on orsupported by the upper bolster plate 62. The second movable forming toolis a part of a floating" assembly mounted between the two bolster plates60, 62 for precision movement along the leader pins 64. The fixedforming member is in the nature of a forming punch and is mounted on acentral portion of the lower bolster plate 60.

For the purpose of better describing the forming equipment in a mannershowing the similarities which exist between the various components, theequipment will be described as being made up of three major componentsconsisting of two movable tool assemblies and a fixed tool assembly. Thebushing housings 66, the bushings 68 therein, the structural portions ofthe bolster plate 62 which rigidly interconnect the bushing housings 66,and the various components of the cavity die tool, including some yet tobe described heating and heat barrier means associated'therewith,together constitute the first movable tool assembly. The second movabletool assembly is the floating" assembly. It comprises a pair of bushingsleeves 74 containing bronze bushings 76 which snugly surroundinglyengage the leader pins 64, a rigid structural portion or cross framewhich spans between the leader pins 64 and rigidly interconnects thebushing housings 74, the forming tool tself, and the heat barrier meansassociated therewith. The three forming tools will now be specificallydescribed in detail.

Each illustrated forming tool comprises an inductively heated core unit.The core units of the two movable tools are basically alike and will bedescribed together. Each comprises a ferromagnetic core 82 of annularchannel form, and an electrical conductor coil embedded in a body 78 ofcast insulation which fills the channel. An annular plate 84 spansacross and covers the open side of the channel 82.

The core unit of the fixed forming tool comprises a block or body 86which includes a girth channel for receiving a conductor coil 88 and abody 90 of cast insulative material in which such coil 88 is embedded.Hard metal die parts 92, 94, 96 are secured to the ferromagnetic coresto be at least primarily conductively heated thereby. It is necessarythat these parts be made of a metal capable of maintaining a hard wearsurface at elevated temperatures. Examples of such metals are HastoloyX, Inconel 750, lnconel 820, and Esco 58, each of which is a nonmagneticmetal.

The lower surface of die part 92 and the upper surface of die part 94are parallel and function as clamping or gripping surfaces. The surfacesof the die part 92 which immediately border and define the centralopening in such part, and the upper and side surfaces of the die part 96are of complementary design and function to form or give shape to theblanks 10.

Each one of the transformers 52 is associated with, and its output isconnected to, a particular one of the three conductor coils 80,80,138.The coils 80, 80, 88 and the associated magnetic cores 82, 82, 86 arefashioned to closely approximate in form the shape of the finished part.The electrical energy conducted to the conductor coils 80, 80, 88 by thetransformers does not directly heat such coils, as in the case ofresistance heater elements, but rather inductively heats the magneticcores 82, 82, 86. Since the conductors 110, 80, 88 are closely adjacentthe conductively heated cores 82, 82, 86, they are susceptible to beingheated by the conduction of heat back from such cores. The conductors80, 80, 88 are protected from such heating to some extent by theinsulative material in which they are embedded. However, the conductors110, 80, 88 are also made of tubular form and a cooling liquid, c.g.water, courses through them for removing the heat which does reach theconductors 80, 80, 88.

As will be evident, the generated heat will be dispersed by conductionthroughout the four cores 82, 82, 86 before being transferred byconduction or otherwise to the die parts 92, 94, 96, contributing to aneven or uniform heating of such parts and the forming surfaces theycarry.

As earlier explained, the bushings 68, 76 which are key elements to theobtainment of a large number of uniform parts throughout a longoperational life of the forming equipment must be operated at relativelylow temperatures. Otherwise the lubricant they employ, and the bushingmaterial itself, will suffer injurious or destructive effects. Accordingto the present invention, a heat barrier is provided to substantiallysurround the heated zone, so as to isolate such zone and localize theheat only where it is desired, while protecting the surrounding parts ofthe forming equipment, especially in the re gion ofthe bushings, frombeing excessively heated.

in the preferred embodiment the heat barrier means for each toolassembly comprises both a thickness of insulative material and a coolantjacket containing passageways through which a cooling fluid is flowed.As best shown by FIG. 3, each movable tool assembly may comprise aboxlike structure formed by four sidewalls and a top and bottom wall,each drilled to include a plurality of passageways for receiving theflowing cooling fluid. The boxlike water jacket of the floating toolassembly is the rigid cross frame which rigidly interconnects orintegrates the two bushing housings 74. lt comprises a bottom plate orwall 98 and four sideplates or walls, two of which are shown and aredesignated 100, 102, respectively. By way ofexample, plurality ofparallel, vertical passageways 104 are drilled in sideplate 100. Shortgrooves 106 are formed in the upper surface of the bottom plate 98 inposition to interconnect the lower ends of the first and secondpassageways 100, the third and fourth passageways, and so on. Abarshaped cap member 108 is secured to the upper edge of plate 100. Itis formed to include short grooves 110 in its lower surface whichinterconnect the upper ends of the second and third passageways 100, thefourth and fifth passageways. and so on. This basic construction,including the use of cap members where needed, is found throughout thecooling jackets of both movable tool assemblies. Copper or rubber tubingconduits 112, or the like, may be connected to corner portions of thecross plates, or to corner portions of the cap members, as shown by HO.4, to serve as supply and discharge conduits for the cooling fluid.

A wall or plank ofinsulation 114 is situated immediately inwardly ofeach sidewall ofthe boxlike cross frame, and a centrally apertured wall116 is interposed between the plate 84 and the bottom wall 98. Thesewalls 114, 116 may be fashioned from a board-type insulation, such asthe ceramic fiber of alumina and silica board made by the CarborundumCompany and sold under the name Fiberfrax, for example.

The water jacket of the upper movable forming tool is also shown to beof boxlike form and to include four side walls, two of which aredesignated 118, 120, in FIG. 3, and a top wall 122. A wall or plankofinsulation 124 is provided immediately inwardly of each sidewall, anda centrally apertured plank 126 is provided immediately inwardly ofthetop plate 122.

The upper bolster plate 62 is shown to include a downwardly openingcentral recess in which the water jacket plate 122 and an upper portionof the sideplates of the water jacket are snugly received. Preferably,as in the ease of the floating tool assembly, the sidewalls and the topwall forming the waterjacket are rigidly secured together to form aboxlike cross frame which rigidly interconnects the bearing housings 66.The bearing housings 66 may include side mounting portions 128, 130which are apertured to receive bolts 132, 134 used for securing thehousing or sleeve 66 to the sidewalls (cg. wall 118 in FlG. 4).

Referring again to FIG. 3, the lower bolster plate 60 may also include acentral recess 136 shaped to snugly receive the lower portion of thefloating tool assembly when it is in its lowermost position. A metallicbaseplate 138 is shown secured to the central portion of the bolsterplate 60, and a grooved plate 140 is shown positioned on the plate 138.The plates 138, 140 together form a cooling jacket for the fixed formingtool assembly. lnlet and outlet means (not shown) are provided fordelivering a cooling fluid (e.g. water) through the passageways 142. Aplank 146 of an insulative material is interposed between the plate 140and the core 86, Anchor bolts 144 are provided for securing together thecoolant jacket plates 138, 140, the insulation 146 and the core 86.Enlarged wells are formed in the plates 138, 140 around the headedportions of the bolts 144, and a castable insulation, such as a castableform of the aforementioned Fiberfrax, for example, is introduced in suchrecesses to surround the headed portions ofthe bolts to form insulationplugs 148. Washers may be provided immediately inwardly of the boltheads to better anchor the bolts in the plugs 148. The insulation plugs148 prevent, or at least minimize, heat conduction from the core 86 intothe bolster plate 60.

The knockout punch or tool 72 is shown to comprise a head 150 and ashank 152. Openings for the shank are provided through the waterjacketplate 122 and the upper bolster plate 62. A cross pin 154, or the like,may be provided for limiting the extend of downward movement of theshank 152, and hence the knockout tool '72 itself. The upper platen 36of the press 14 is shown to be composed of a top plate 156 spaced abovea lower plate 158 by spacer blocks or plates 160 arranged to provide acentral recess 162 in the upper platen 136 about the upper end of theshank 152. A side tunnel is pro vided so that a hand tool may beinserted into the recess 162 and used to depress and operate theknockout tool.

Two or more sets of bores are provided through the lower bolster plate60 and the lower platen 32, in parallelism with the guide or leader pins64, to each receive a support pin 164 which rests at its upper endagainst the lower surface of the floating tool assembly and at its lowerend against the upper surface of the support pad 48. It is through theintermediacies of the support pins 164 that the secondary ram 44 exertsa biasing force on the floating tool assembly. A wear plate 166 ofstainless steel or some other hard and durable metal may be provided onthe underside of the floating tool assembly to be the part thereofthatis immediately contacted by the pins 164.

As should be apparent by now, the isolation of the generated heat by theinsulation 114, 116, 124, 126, 146 into the central region of theforming equipment, and the removal ofsuch heat from such central regionby means of the coolant jackets 93,100,102,118, 122, 124, 140, is whatmakes possible the use of the leader pins 64 and the bushings 68, 76 foraccurately guiding the two movable forming tools. A further advantageousresult ofthe use and particular placement of the insulation is that itreduces the amount of exposed surface on each of the cores. and thusreduces the amount of oxidation that takes place on the cores duringheating.

In operation, the lubricated and possibly preheated blank 10 is placedin the forming equipment between the two movable forming tools (FIG. 9),and if not already preheated is preheated in the forming equipment.Hydraulic fluid is then 99 to the secondary ram 44 to cause it, throughthe intermediacy of the support pins 164, to raise the floating toolassembly. Fluid is also delivered into the main ram 40 to cause alowering of the upper platen 36, and the upper forming tool carriedthereby. A larger force is intentionally developed by the main ram 40 sothat it will override the secondary ram 44, causing the two movableforming tools and the blank 10 clamped between them to be moveddownwardly the the punch. The force differential is regulated so that asufficient holding pressure is maintained between the holding surfacesof the plates 92, 94 and the portion of the blank 10 sandwiched betweenthem. Preferably, the two rams 40, 44 are conjunctively operated bymaintaining a constant fluid pressure in the cylinder of the upper ram40 above the piston therein, while slowly bleeding fluid from below suchpiston. At the same time, a constant pressure is maintained in thecylinder of the lower ram 44, below the piston therein, while the spaceabove such piston is vented. The force differential which causesdownward movement of the movable tools and the blank is regulated bysuch bleeding of fluid from below the upper piston. This arrangementresults in a substantially jerk-free downward movement of the blank 10.The pressure developed between the holding surfaces of the plates 92, 94is sufficient to prevent wrinkling, but insufficient to prevent theblank aided by the lubricant coating from sliding sideways of the pressas the part is being formed. Downward movement of the blank (i.e. thebleeding rate) is carefully controlled so that plastic deformation ofthe blank 10 occurs unattended by any appreciable strain hardeningthereof.

If for any reason it becomes necessary to look at the part being formedprior to completion thereof, bleeding of fluid from the upper cylinderis ceased and the upper ram 40 is reversed to lift the upper platen 36and the die assembly carried thereby. Then, when it is desired to resumethe forming process, fluid flow to the upper ram 40 is again reversed tocause a lowering of the platen 36 and the die assembly. Once the dieassembly is back in mating engagement with the partially formed part,bleeding of fluid from below the upper piston is once again started andcontinued until the part is fully formed (FIG. 11).

Following forming of the part 10 the two movable tools are raised untilthe support pad is in the position shown by FIG. 12, and the upperplaten and the die assembly carried thereby are by themselves raised anadditional amount. Next, the knockout tool 72 is depressed, such as bymeans ofa hand tool introduced through the side tunnel into the recess162, as earlier explained. The part is then ready to be grasped by meansof a pair of tongs or the like and moved to a cooling station, e.g. thepostheat oven 16, as earlier explained.

In FIGS. 9-12 the insulation blankets have been omitted and the coolantjackets have not been detailed, for simplicity of illustration.

FIGS. 7 and 8 relate to a modified form of forming equipment which isadapted for forming a part 10 of the type shown by FIG. 6. Suchequipment includes a lower fixed bolster plate 166, a pair ofleader pins168 extending upwardly therefrom, and an upper movable bolster plate170. The upper bolster plate 170 carries a movable forming tool or die172, shown to comprise a metallic cross frame which also serves as acoolant jacket. Such cross frame is shown to include a rear wall 174, atop wall 176, and end walls 178, 180. The walls 172, 178, 180 are formedto include a plurality or relatively closely spaced vertical passageways188, and the top panel 176 is formed to include a plurality of closelyspaced horizontal passageways 190. As in the earlier embodiment, capmember 182, 184, 186 are provided to border the longitudinal edges ofthe plates 174, 176. The corner cap member 182 may be provided withintersecting bores 192, 194 which together form a right-angledpassageway for interconnecting the upper ends of passageways 188 withthe adjacent ends of passageways 190. Cap member 184 includes aplurality of short grooves 196 which serve to interconnect the oppositeends of the passageways 190 in a pattern of pairs. Similarly, cap member186 includes a plurality of short grooves 198 which serve tointerconnect the lower ends of the passageways 188 in groups of pairs.An inlet 200 may be provided in end wall 178 and an outlet 202 in endwall 180, to complete with the various passageways and grooves acontinuous flow path for the coolant (e.g. water) through the coolantjacket.

In this embodiment the bolster plate is shown to include integrallyformed bushing housings 204, 206 which include bushings 208, 210 servingto mount the bolster plate 170 and the forming tool carried thereby forprecision movement up and down along the leader pins 168. Thus, in thisembodiment it is the bolster plate 170 itself which constitutes thecross frame means which rigidly interconnects the bushing housings204,206.

A plank of board insulation 212 is situated immediately below the topplate 176, and a smaller board of insulation 214 is positionedimmediately inwardly of the portion of plate 176 which extends below thelower surface of plank 212. Similarly, planks 216, 218 of insulation areprovided at the two ends of the assembly immediately inwardly of the endwalls 178, 180.

The forming tool 220 itself is located within a generally squarecornered nook bounded on top by the insulation plank 212, at the rear byinsulation plank 214 and at the ends by insulation planks 216, 218. Suchtool is shown to comprise a core assembly composed of main body 222about which has been formed a girth channel, and a rear plate 224positioned between the body 222 and the insulation 214. The girthchannel is filled with insulative material, which is preferably cast inplace. A coil 228 of copper tubing or some other suitable tubularconductor material is embedded within the insulation 226. A hard metaldie part 230 is secured to the body 222 and the plate 224.

The second or floating movable tool assembly is basically similar to thejust-described tool assembly. Hence, it will not be described in asgreat detail. It comprises a coolant jacket composed of a rear wall 232,a lower wall 234, end walls 236, 238, and edge caps 240, 242, 244. Insuch assembly, the bearing housings or sleeves 246, 248 (FIG. 7) aresecured to the end walls 236, 238, and the coolant jacket serves as acrossframe which structurally interconnects the two housings 246, 248.In FIG. 7, the bushing 250 in housing 246 is shown in section, whereasthe bushing 252 in the opposite housing 248 merely has its positionindicated by broken or hidden lines.

The insulation jacket of the floating tool assembly comprises a rearplank 254, a lower plank 256, and end planks 258, 260. The tool itselfincludes a body 262 formed to include a girth channel, a member 264interposed between plank 254 and body 262, and a die part 266. The girthchannel is filled with insulation 268 in which is embedded a conductorcoil 270.

A hard metal wear plate 272 may be provided below coolant jacket member234 to serve as a contact plate for the support pins 164.

In FIG. 8 a guide bracket 274 is shown positioned to the rear of thepath of movement of the two movable tool assemblies. It is shown toinclude a wear plate 276 of a hard metal which in use is contacted by asimilar plate 278 provided to the rear of coolant jacket member 174 ofthe upper movable tool assembly.

The equipment also comprises a fixed forming tool or die 280 which issimilar in basic construction to the two movable tools. It includes acoolant jacket formed by a bottom plate 282, a front plate 284, endplates 286, 288, and cap members 290, 292, 294. Passageways are providedin the parts 282, 284,286, 288 and grooves in the parts 290, 292 to alltogether form a continuous passageway for a flowing coolant. Suchassembly also includes an insulation jacket composed of a front plank296, a lower plank 298, and two end planks 300, 302. The tool itselfcomprises a body 304 which like the bodies llll 222, 262 includes agirth channel for receiving insulative material 306 in which is embeddeda coil 308 ofcopper tubing or some other suitable tubular conductor. Aplate 310 is interposed between the body 304 and the insulation plank296, and a hard metal die part 312 is secured to the top of body 304.

Die parts 230, 312 carry complementary forming surfaces. Locator pins314 are carried by die part 312. Die part 266 serves primarily as aholding member.

In operation of the forming equipment shown by FIGS. 7 and 8, the blanks10 are successively placed on the upper surface of die part 266 and incontact with the locating pins 314 (see FlG. 13). The two rams 40, 44 ofthe press 14 are operated as in the operation of the first embodiment tofirst cause a clamping of the blank 10 between the clamping surfaces ofthe die parts 230, 266, and then a downward movement of the two movabletool assemblies relative to the fixed tool assembly. As before, care istaken to see that the heated blank (cg. to temperature of l,OO0l.775 F.)is slowly moved relative to the fixed forming tool. The action desiredis a wiping" action in which the metal is slowly moved and reformed tocause a plastic deformation unattended by any appreciable strainhardening.

A heel block 316 is positioned forwardly ofthe fixed tool assembly andserves to support and prevent a forward movement of the fixed toolassembly during the forming operation. At the rear of the equipment, thetight engagement made between the wear plates 276,278 braces the twomovable tool assemblies against an unwanted turning movement as a resultof the forces imposed on them during the forming operation.

In either type of forming apparatus each forming tool is independentlyheated by one ofthe transformers 52 and is independently controlled asto temperature The control circuitry (not shown) for each conductor coilincludes a temperature sensor or measuring device (e.g. a thermocouple)which measures the temperature of the die part with which such coil isassociated. When forming titanium, at least, the fixed tool is operatedat a lower temperature (e.g. about 50l00 F. lower) than the temperatureof the two movable tools which are maintained together at about the sametemperature. This differential heating results in the portion of thetitanium (or other metal) blank which is held or clamped between the twohigher temperature movable parts being heated a greater amount so as tobe more ductile than the portion ofsuch blank which is in contact withthe punch or fixed tool. As a con sequence, during forming there is agreater tendency for metal flow to occur in the clamped region than inthe region contoured by the punch, resulting in a minimization ofthinning in the region of the finished part which is contacted by thepunch. For most titanium alloy forming the punch may be heated to atemperature within the range of l300- l400 F. and the two movable toolsheated to a temperature within the range of 14001500 Alpha-Beta titaniumcan be hardened by first forming the part at a higher temperaturefollowed by water or like quenching. To effect such heating the punchmay be heated to a temperature within the range of l725 1 750 F., andthe two movable tools to a temperature within the range of l750l775 F. Acoated part is first drawn and then held in the press for about 15-2Oseconds to assure even heating at this level. Next, the press is openedand the part is removed and quickly quenched, as in water at roomtemperature. The part is then aged in a furnace at about 1000 F.,containing an inert, e.g. argon, atmosphere for about 4 hours. lNsteadof forming at the 1700 F. level the forming may be done at a lowertemperature and then be followed by a heating of the formed part in thepress or in an oven up to a temperature above the temperature requiredfor hardening.

While various forms of forming equipment embodying principles of theinvention and a preferred method have been described, it is to beunderstood that changes in construction and technique may be madewithout departing from the principles of the invention. Accordingly. thescope of the invention is to be determined solely by the scope andproper interpretation ofthe following claims.

What 1 claim is:

1. A method of forming a part from a sheet metal blank in a formingpress which includes a fixed forming tool and two movable forming tools,supported by leader pins and bushings for precision movement along apath bordering the fixed forming tool, in which each said tool includesa mass which is capable of being heated by induction, comprising:

placing a first portion ofthe blank between the two movable formingtools and an adjacent second portion ofthe blank in position to contactthe fixed forming tool; moving the two movable forming tools relativelytogether to firmly clamp the first portion of said blank between them;

using induction heating coils which surround portions of said toolmasses to inductively heat each of said forming tools to a temperaturesufficient to cause them to in turn conductively heat the blank andmaintain it at forming temperature, while maintaining said leader pinsand bushings relatively cool, so that they can function properlythroughout a long life ofrepetitious use; and

moving the two movable forming tools and the blank clamped between them,as an assembly, relatively towards the fixed forming tool, and the blankagainst such tool, at a rate causing plastic deformation of the blankattended by no appreciable strain hardening.

2. The method of claim 1, including circulating a cooling fluid throughat least a portion of the region containing the inductively heatedforming tools and the guide pins and bushings, to remove heat from suchregion which, if not removed, would tend to harmfully heat such guidepins and bushings.

3. The method of claim 1, further comprising preheating the blank toabout its forming temperature before placing it in the forming press.

4. The method of claim 1, further comprising preheating the blank toabout its forming temperature in a substantially airfree atmospherebefore placing it in the forming press.

5. The method of claim 1, further comprising coating the blank with ahigh temperature lubricant before placing it in the forming press, saidlubricant serving to facilitate some slippage ofthc clamped portion ofthe blank during its forming.

6. The method of claim 5, further comprising preheating the coated blankin a substantially nitrogen-free atmosphere.

7. The method of claim 1, comprising slowing cooling the formed part toprevent severe surface cracking.

The method of claim 7 comprising slowly cooling the formed part in asubstantially air-free atmosphere.

9. The method of claim 7 comprising cooling the formed part by firstplacing it in a heated confined zone the temperature ofwhich is belowthe forming temperature but above ambient temperature, allowing it toslowly and naturally cool in said zone down to the temperature of thezone, and then placing such part in a nonheated zone and allowing it toslowly and naturally cool in said zone down to ambient temperature.

10. The method of claim 1, applied to a titanium metal containing blankand wherein the forming tools are inductively heated to a temperatureenabling them to conductively heat the blank to about l00O- 1 775 F.

11. A method of forming a part from a sheet metal blank in a formingpress which includes a fixed forming tool and two movable forming toolssupported for movement along a path bordering the fixed forming tool,comprising:

placing a first portion ofthe blank between the two movable formingtools and an adjacent second portion ofthe blank in position to contactthe fixed forming tool; moving the two movable forming tools relativelytogether to firmly hold the first portion of said blank between them;

inductively heating each of said forming tools to a temperaturesufficient to cause them to in turn conductively heat the blank andmaintain it at forming temperature, including heating the two movabletools, and hence the held portion of the blank, to a higher temperaturethan the fixed forming tool and the unheld portion of the blank which isheated thereby; and

moving the two movable forming tools and the blank held between them, asan assembly, relatively towards the fixed forming tool, and the blankagainst such tool, at a rate causing plastic deformation of the blankattended by no appreciable strain hardening, with the greater heating ofthe held portion causing more material flow to occur in such portionthan in the lower temperature unheld portion of the blank, resulting ina minimization of thinning in the contoured region ofthe finished part.

12. The method of claim 11, wherein a titanium alloy blank is used andthe forming tools are inductively heated to a temperature enabling themto conductively heat the blank to about l000l775 F., and a -200 F.temperature differential is maintained between the portions of the blankheated by the movable and fixed tools.

13. The method of claim 12, wherein the titanium alloy is temperable andsaid method includes heating the formed part to a suitable temperaturefor hardening and then while still hot quenching it in water of thelike.

14. The method of claim 11, further comprising coating the blank with ahigh-temperature lubricant and preheating it to about its formingtemperature, said lubricant serving both as a protective coating, toprotect the metal against corrosion, and as a lubricant to facilitatesome slippage of the held portion of the blank during forming.

15. Sheet metal forming equipment comprising:

a first bolster plate;

a plurality of spaced-apart leader pins, each of which is firmly securedat one of its ends to said first bolster plate and extends away fromsaid plate, in parallelism with each other leader pin;

a first forming tool assembly secured to said bolster plate on the sameside thereofas said leader pins, said assembly including an inductivelyheatable mass, an induction heating coil surrounding a portion of saidmass, a die part on said mass, and heat barrier means interconnectedbetween said mass and said bolster plate, and

a second bolster plate including bushing means mounting it for precisionmovement along said leader pins;

a second-forming tool assembly secured to said second bolster plate, onthe side thereof facing the first forming tool assembly, and comprisingan inductively heatable mass, and induction heating coil surrounding aportion of said mass, a die part on said mass, and heat barrier meansinterconnected between said heated mass and said bolster plate, saidheat barrier means extending between said mass and said bushing meansfor protecting the bushing means against overheating, with the die partof the second forming tool assembly cooperating with the die part of thefirst forming tool assembly when the bolster plates are moved relativelytogether to impress a shape into a sheet metal blank inserted betweenthem.

16. The sheet metal forming equipment of claim 15, wherein each saidinduction heating coil comprises electrical conductors of tubular form,so that a cooling fluid can be circulated through them.

17. The sheet metal forming equipment of claim 15, wherein saidequipment further comprises a third forming tool assembly interposedbetween said first and second bolster plates and including:

a bushing housing for each leader pin, said housings containing guidebushings which surroundingly engage said leader pins;

support means rigidly interconnecting said bushing housings; and

a third forming tool assembly secured to said support means, on the sidethereof forming the second forming tool assembly, and comprising aninductively heatable mass, a die part on said mass, and an inductionheating coil surrounding a portion of said mass, with said leader pins,guide bushings, the second bolster plate and said support means servingto mount the second and third forming tool assemblies for precisionmovement along a 8path bordering the first forming assembly. 1 The sheetmetal formmg equipment of claim 17, further comprising first, second andthird independently controllable means for supplying electrical energyto the induction heating coils of said first, second and third formingtool assemblies, enabling the second and third assemblies to be controlheated at a higher temperature than the first assembly.

19. The sheet metal forming equipment of claim 15, wherein each saidheat barrier means includes a coolantjacket containing passagewaysthrough which a cooling fluid may be flowed.

20. The sheet metal equipment of claim 15, wherein each said formingtool assembly comprises sidewall means, and said heat barrier meanscomprises insulative material interposed between said sidewall means andthe forming tool.

21. The sheet metal equipment of claim 20, wherein said bushing meanscomprise sleeve members situated outwardly of, and rigidly secured to,the sidewall means of said second forming tool assembly.

22. The sheet metal forming equipment ofclaim 15, in combination with aforming press including a fixed platen, a movable platen, and means forremovably securing one of said bolster plates to one of said platens andthe other bolster plate to the other platen.

23. The sheet metal forming equipment of claim 17, wherein said firstbolster plate includes at least one support pin opening extendingthrough it in parallelism with said leader pins, and said equipmentfurther includes:

a support pin extending through said opening, and at one end containingthe support means of said third forming tool assembly;

a first piston-cylinder motor connected to said second bolster plate,for moving it towards and away from said first bolster member; and

a second piston-cylinder motor for moving said third forming toolassembly through the intermediary of said support pin.

24. Sheet metal forming equipment comprising:

a fixed forming tool and two movable forming tools supported formovement with a clamped portion of a sheet metal blank between themalong a path bordering the fixed forming tool, with each said formingtool comprising a die member and an induction heating coil associatedwith said member; and

first, second and third independently controllable means for supplyingelectrical energy to the induction heating coils of said fixed and saidtwo movable forming tools, enabling the two movable die members to becontrol heated at a higher temperature than the fixed die member.

25. Sheet metal forming equipment according to claim 24, wherein eachdie member comprises an inductively heatable mass, and wherein eachinduction heating coil surrounds a portion of said mass, with saidinduction heating coils in use inductively heating said masses, and withsaid die members conductively heating material to be formed which is incontact with said members.

26. Sheet metal forming equipment according to claim 24, wherein eachinduction heating coil comprises electrical conductors of tubular form,so that a cooling fluid can be flowed through them, and wherein saidequipment further comprises means for delivering a cooling fluid intosaid conductors.

2. The method of claim 1, including circulating a cooling fluid throughat least a portion of the region containing the inductively heatedforming tools and the guide pins and bushings, to remove heat from suchregion which, if not removed, would tend to harmfully heat such guidepins and bushings.
 3. The method of claim 1, further comprisingpreheating the blank to about its forming temperature before placing itin the forming press.
 4. The method of claim 1, further comprisingpreheating the blank to about its forming temperature in a substantiallyair-free atmosphere before placing it in the forming press.
 5. Themethod of claim 1, further comprising coating the blank with a hightemperature lubricant before placing it in the forming press, saidlubricant serving to facilitate some slippage of the clamped portion ofthe blank during its forming.
 6. The method of claim 5, furthercomprising preheating the coated blank in a substantially nitrogen-freeatmosphere.
 7. The method of claim 1, comprising slowing cooling theformed part to prevent severe surface cracking.
 8. The method of claim7, comprising slowly cooling the formed part in a substantially air-freeatmosphere.
 9. The method of claim 7, comprising cooling the formed partby first placing it in a heated confined zone the temperature of whichis below the forming temperature but above ambient temperature, allowingit to slowly and naturally cool in said zone down to the temperature ofthe zone, and then placing such part in a nonheated zone and allowing itto slowly and naturally cool in said zone down to ambient temperature.10. The method of claim 1, applied to a titanium metal containing blankand wherein the forming tools are inductively heated to a temperatureenabling them to conductively heat the blank to about 1000*-1775* F. 11.A method of forming a part from a sheet metal blank in a forming presswhich includes a fixed forming tool and two movable forming toolssupported for movement along a path bordering the fixed forming tool,comprising: placing a first portion of the blank between the two movableforming tools and an adjacent second portion of the blank in position tOcontact the fixed forming tool; moving the two movable forming toolsrelatively together to firmly hold the first portion of said blankbetween them; inductively heating each of said forming tools to atemperature sufficient to cause them to in turn conductively heat theblank and maintain it at forming temperature, including heating the twomovable tools, and hence the held portion of the blank, to a highertemperature than the fixed forming tool and the unheld portion of theblank which is heated thereby; and moving the two movable forming toolsand the blank held between them, as an assembly, relatively towards thefixed forming tool, and the blank against such tool, at a rate causingplastic deformation of the blank attended by no appreciable strainhardening, with the greater heating of the held portion causing morematerial flow to occur in such portion than in the lower temperatureunheld portion of the blank, resulting in a minimization of thinning inthe contoured region of the finished part.
 12. The method of claim 11,wherein a titanium alloy blank is used and the forming tools areinductively heated to a temperature enabling them to conductively heatthe blank to about 1000*-1775* F., and a 25*-200* F. temperaturedifferential is maintained between the portions of the blank heated bythe movable and fixed tools.
 13. The method of claim 12, wherein thetitanium alloy is temperable and said method includes heating the formedpart to a suitable temperature for hardening and then while still hotquenching it in water of the like.
 14. The method of claim 11, furthercomprising coating the blank with a high-temperature lubricant andpreheating it to about its forming temperature, said lubricant servingboth as a protective coating, to protect the metal against corrosion,and as a lubricant to facilitate some slippage of the held portion ofthe blank during forming.
 15. Sheet metal forming equipment comprising:a first bolster plate; a plurality of spaced-apart leader pins, each ofwhich is firmly secured at one of its ends to said first bolster plateand extends away from said plate, in parallelism with each other leaderpin; a first forming tool assembly secured to said bolster plate on thesame side thereof as said leader pins, said assembly including aninductively heatable mass, an induction heating coil surrounding aportion of said mass, a die part on said mass, and heat barrier meansinterconnected between said mass and said bolster plate; and a secondbolster plate including bushing means mounting it for precision movementalong said leader pins; a second-forming tool assembly secured to saidsecond bolster plate, on the side thereof facing the first forming toolassembly, and comprising an inductively heatable mass, and inductionheating coil surrounding a portion of said mass, a die part on saidmass, and heat barrier means interconnected between said heated mass andsaid bolster plate, said heat barrier means extending between said massand said bushing means for protecting the bushing means againstoverheating, with the die part of the second forming tool assemblycooperating with the die part of the first forming tool assembly whenthe bolster plates are moved relatively together to impress a shape intoa sheet metal blank inserted between them.
 16. The sheet metal formingequipment of claim 15, wherein each said induction heating coilcomprises electrical conductors of tubular form, so that a cooling fluidcan be circulated through them.
 17. The sheet metal forming equipment ofclaim 15, wherein said equipment further comprises a third forming toolassembly interposed between said first and second bolster plates andincluding: a bushing housing for each leader pin, said housingscontaining guide bushings which surroundingly engage said leader pins;support means rigidly interconnecting said bushing housings; and a thirdforming tool assembly secured to said support means, on the side thereofforming the second forming tool assembly, and comprising an inductivelyheatable mass, a die part on said mass, and an induction heating coilsurrounding a portion of said mass, with said leader pins, guidebushings, the second bolster plate and said support means serving tomount the second and third forming tool assemblies for precisionmovement along a path bordering the first-forming assembly.
 18. Thesheet metal forming equipment of claim 17, further comprising first,second and third independently controllable means for supplyingelectrical energy to the induction heating coils of said first, secondand third forming tool assemblies, enabling the second and thirdassemblies to be control heated at a higher temperature than the firstassembly.
 19. The sheet metal forming equipment of claim 15, whereineach said heat barrier means includes a coolant jacket containingpassageways through which a cooling fluid may be flowed.
 20. The sheetmetal equipment of claim 15, wherein each said forming tool assemblycomprises sidewall means, and said heat barrier means comprisesinsulative material interposed between said sidewall means and theforming tool.
 21. The sheet metal equipment of claim 20, wherein saidbushing means comprise sleeve members situated outwardly of, and rigidlysecured to, the sidewall means of said second forming tool assembly. 22.The sheet metal forming equipment of claim 15, in combination with aforming press including a fixed platen, a movable platen, and means forremovably securing one of said bolster plates to one of said platens andthe other bolster plate to the other platen.
 23. The sheet metal formingequipment of claim 17, wherein said first bolster plate includes atleast one support pin opening extending through it in parallelism withsaid leader pins, and said equipment further includes: a support pinextending through said opening, and at one end containing the supportmeans of said third forming tool assembly; a first piston-cylinder motorconnected to said second bolster plate, for moving it towards and awayfrom said first bolster member; and a second piston-cylinder motor formoving said third forming tool assembly through the intermediary of saidsupport pin.
 24. Sheet metal forming equipment comprising: a fixedforming tool and two movable forming tools supported for movement with aclamped portion of a sheet metal blank between them along a pathbordering the fixed forming tool, with each said forming tool comprisinga die member and an induction heating coil associated with said member;and first, second and third independently controllable means forsupplying electrical energy to the induction heating coils of said fixedand said two movable forming tools, enabling the two movable die membersto be control heated at a higher temperature than the fixed die member.25. Sheet metal forming equipment according to claim 24, wherein eachdie member comprises an inductively heatable mass, and wherein eachinduction heating coil surrounds a portion of said mass, with saidinduction heating coils in use inductively heating said masses, and withsaid die members conductively heating material to be formed which is incontact with said members.
 26. Sheet metal forming equipment accordingto claim 24, wherein each induction heating coil comprises electricalconductors of tubular form, so that a cooling fluid can be flowedthrough them, and wherein said equipment further comprises means fordelivering a cooling fluid into said conductors.